Vladimir Putin probably approved Russian intelligence operation to murder Alexander Litvinenko, inquiry finds
* Kremlin-approved spy operation killed Litvinenko - inquiry
* Putin probably approved the FSB kill operation - inquiry
* Russians Lugovoy and Kovtun carried out the murder - inquiry
* Kremlin has always denied involvement
* Lugovoy says accusation is absurd
President Vladimir Putin probably approved a 2006 Russian intelligence operation to murder ex-KGB agent Alexander Litvinenko with radioactive polonium-210 in London, a British inquiry concluded, prompting a row with Moscow.
Russia, which had declined to cooperate in the inquiry, described Britain's handling of the case as opaque and biased.
Litvinenko, 43, an outspoken critic of Putin who fled Russia for Britain exactly six years to the day before he was poisoned, died after drinking green tea laced with the rare radioactive isotope at London's Millennium Hotel.
An inquiry led by senior British judge Robert Owen found that former KGB bodyguard Andrei Lugovoy and another Russian, Dmitry Kovtun, carried out the killing as part of an operation probably directed by Russia's Federal Security Service (FSB), the main heir to the Soviet-era KGB.
"The FSB operation to kill Mr Litvinenko was probably approved by Mr Patrushev, then head of the FSB, and also by President Putin," Owen said.
"I have concluded that there is a strong probability that when Mr Lugovoy poisoned Mr Litvinenko, he did so under the direction of the FSB. I have further concluded that Mr Kovtun was also acting under FSB direction," he said.
The death of Litvinenko marked a post-Cold War low point in Anglo-Russian relations, and ties have never recovered, marred further by Russia's annexation of Crimea and its support for Syrian President Bashar al-Assad.
The British government said it would summon Russia's ambassador.
"The conclusion that the Russian state was probably involved in the murder of Mr Litvinenko is deeply disturbing," interior minister Theresa May told parliament.
"This was a blatant and unacceptable breach of the most fundamental tenets of international law and of civilised behaviour."
The image of Litvinenko lying on his bed at London's University College Hospital, cadaverous and having lost his hair, was emblazoned across British and other Western newspapers and later shown to the inquiry. He took over three weeks to die.
The Kremlin has always denied any involvement but the claim that Putin directly ordered a killing of an opponent with a radioactive isotope in a major Western capital provoked immediate censure from Moscow.
Russia's Foreign Ministry said what it called Britain's politicised, biased and opaque handling of the Litvinenko case had clouded relations.
From his deathbed, Litvinenko told detectives he believed Putin had directly ordered his killing. The Kremlin dismissed that accusation at the time as absurd.
The judge said he was sure Lugovoy and Kovtun had placed the polonium 210 in a teapot at the Millennium Hotel's Pine Bar on Nov. 1, 2006. Traces of the highly radioactive substance were found at several sites across the city including offices, hotels, planes and Arsenal soccer club's Emirates Stadium.
Russia declined to participate in the six-month British inquiry, as did Lugovoy and Kovtun, the two Russian men who met with Litvinenko in London.
Both Lugovoy and Kovtun have previously denied involvement and Russia has refused to extradite them. Lugovoy was quoted by the Interfax news agency as saying the accusation was absurd.
Owen cited several reasons why the Russian state would have wanted Litvinenko dead.
The ex-spy was regarded as having betrayed the FSB by accusing it of 1999 apartment block bombings that killed more than 200 and which Moscow, launching an offensive to restore control over the southern region of Chechnya, blamed on Chechens. The FSB also had information Litvinenko had started working for British intelligence.
He was also close to leading dissidents and opponents of Putin and his administration who he had accused of collusion with organised crime.
"There was undoubtedly a personal dimension to the antagonism between Mr Litvinenko on the one hand and President Putin on the other," Owen's report said.
Some of the inquiry was held in secret and evidence from the British government and spy agencies has not been publicly disclosed. Owen said this information had helped form his conclusions which were contained in his 326-page report.
Litvinenko's widow, Marina, whose persistence led to the inquiry being held, called for Russian spies to be kicked out of Britain and for sanctions against Russia.
"I'm calling immediately for exclusion from the UK of all Russian intelligence operatives whether from the FSB, who murdered Sasha, or from other Russian agencies based in the London embassy," she said outside London's Royal Courts of Justice.
"I'm also calling for the imposition of targeted economic sanctions and travel bans against named individuals, including Mr Patrushev and Mr Putin," she said, adding that the British government had promised action.